If you're going to work with that book, you should brush up on Sumerian myth and belief. It is the more believable of the Necromonicons. H.P. Lovecraft's is entirely fiction and many others decided to create their own to cash in on the profit. However Simon's version is neither proven nor disproven to be an authentic workable magic system. But you must be aware, regardless you are working with one of the oldest interpretations of higher beings. Misuse could be disasterous.